Chlamydia is the most commonly diagnosed STI in the UK. It's most common in men and women under the age of 25. You don't need to have lots of sexual partners to be at risk.

Chlamydia is caused by a bacterium called Chlamydia trachomatis, which is found in the semen of men and the vaginal fluids of women who have the infection. If you or your sexual partners are infected and don't get treatment, chlamydia can spread to other parts of the body and cause pain, especially in the abdomen.

It may lead to infertility (not being able to have children). You can get chlamydia by having unprotected (without a condom) vaginal, anal or oral sex with someone who is already infected. It can also be passed on by sharing sex toys which haven't been washed or covered with a condom before each use. It can also be passed by a pregnant woman to her baby during pregnancy or at the birth.

getting tested

If you're under the age of 25 and sexually active you should be tested for chlamydia every year, or if you meet a new partner.

Many places offer chlamydia testing as part of the NHS National Chlamydia Screening Programme (NCSP), including GP surgeries, sexual health clinics and community pharmacies.The test as part of the NHS National Chlamydia Screening Programme is free, simple, painless and confidential.

You can do the test yourself and you don't need to be examined. Men give a urine sample. Women may be asked either to give a urine sample or to take a swab. Women take the swab themselves from the lower vagina. The swab or urine test is sent away for analysis. It can take up to 10 days for the results to come through. It's very rare for chlamydia tests to be wrong.

Outside of the NCSP, the test may be carried out in different ways depending on where you have it done, but the staff will explain this to you.

To find out about getting tested in your area click on 'find an outlet', select your Borough and then click 'Chlamydia Screening' (in the links menu).

symptoms

Most people with chlamydia have no symptoms. People who develop symptoms may notice them one to three weeks after contact with chlamydia, or many months later, or not until the infection spreads. If you have any of these symptoms, visit your GP or a sexual health clinic straight away.

Women may notice:

unusual vaginal discharge

bleeding between periods

bleeding after sex

heavier periods (including women who are using hormonal contraception)

pain (or bleeding) during sex

pain when passing urine

lower abdominal (pelvic) pain

Men may notice:

a white/cloudy or watery discharge from the penis

burning and itching in the genital area

pain when passing urine

painful swelling of the testicles

For both men and women:

If the infection is in the rectum, there are rarely symptoms but it can sometimes cause discomfort and discharge.

Infection in the eyes can cause symptoms including pain, swelling, irritation and discharge.